Excimer-laser deinsulation of Parylene-C coated Utah electrode array tips

Utah electrode arrays (UEAs) are highly effective to measure or stimulate neural action potentials from the central or peripheral nervous system. The measured signals can be used for applications including control of prosthetics (recording) and stimulation of proprioceptive percepts. The UEAs are coated with biocompatible Parylene-C, and the electrode tips are deinsulated to expose the active electrode coated with sputtered iridium oxide films (SIROFs) to transduce neural signals. In conventional UEA technology, the electrode tips are deinsulated by poking the electrodes through aluminum foil followed by an oxygen plasma etch of the exposed areas. However, this method suffers from lack of uniformity and repeatability and it is time consuming. We focus on laser tip-deinsulation technology that can provide a repeatable, uniform, and less time consuming tip exposure for UEAs. The laser deinsulated SIROF area is characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), and by measuring the impedance of the exposed sites. The value of impedance and XPS peaks showed that the Parylene was clearly removed. The damage induced by laser irradiation on the SIROF film was also investigated to understand the selectivity of laser deinsulation. Thicker SIROF films showed better resistance to fracture. The results indicate that laser deinsulation is an effective method to etch Parylene films.